Wireless communication systems, including cellular phones, paging devices, personal communication services (PCS) systems, and wireless data networks, have become ubiquitous in society. Wireless service providers continually try to create new markets for wireless devices and to expand existing markets by making wireless devices and services cheaper and more reliable. The price of end-user wireless devices, such as cell phones, pagers, PCS systems, and wireless modems, has been driven down to the point where these devices are affordable to nearly everyone and the price of a wireless device is only a small part of the end-user's total cost. To continue to attract new customers, wireless service providers concentrate on reducing infrastructure costs and operating costs, and on increasing handset battery lifetime, while improving quality of service in order to make wireless services cheaper and better.
To maximize usage of the available bandwidth, a number of multiple access technologies have been implemented to allow more than one subscriber to communicate simultaneously with each base station (BS) in a wireless system. These multiple access technologies include time division multiple access (TDMA), frequency division multiple access (FDMA), and code division multiple access (CDMA). These technologies assign each system subscriber to a specific traffic channel that transmits and receives subscriber voice/data signals via a selected time slot, a selected frequency, a selected unique code, or a combination thereof.
CDMA technology is used in wireless computer networks, paging (or wireless messaging) systems, and cellular telephony. In a CDMA system, mobile stations and other access terminals (e.g., pagers, cell phones, laptop PCs with wireless modems) and base stations transmit and receive data on the same frequency in assigned channels that correspond to specific unique orthogonal codes. For example, a mobile station may receive forward channel data signals from a base station that are encoded, formatted, interleaved, spread with a Walsh code and a long pseudo-noise (PN) sequence. In another example, a base station may receive reverse channel data signals from the mobile station that are encoded, block interleaved, modulated, and spread with a spreading code derived from the mobile station identification number prior to transmission by the mobile station. The data symbols following interleaving may be separated into an in-phase (I) data stream and a quadrature (Q) data stream for QPSK modulation of an RF carrier. One such implementation is found in the TIA/EIA-95 CDMA standard (also known as IS-95). Another implementation is the TIA/EIA-2000 standard (also known as IS-2000).
The current generation of cellular phones is used primarily for voice conversations between a subscriber device (or wireless device) and another party through the wireless network. A smaller number of wireless devices are data devices, such as personal digital assistants (PDAs) equipped with cellular/wireless modems. Because the bandwidth for a current generation wireless device is typically limited to a few tens of kilobits per second (kbps), the applications for the current generation of wireless devices are relatively limited. However, this is expected to change in the next (or third) generation of cellular/wireless technology, sometimes referred to as “3G” cellular/wireless, where much greater bandwidth will be available to each wireless device (i.e., one hundred fifty three and six tenths kilobits per second (153.6 kbps) or greater). The higher data rates will make Internet applications for wireless devices much more common. For instance, a 3G cellular telephone (or a PC with a 3G cellular modem) may be used to browse web sites on the Internet, to transmit and receive graphics, to execute streaming audio or video applications, and the like. A much higher percentage of the wireless traffic handled by 3G cellular systems will be Internet protocol (IP) traffic and a lesser percentage will be traditional voice traffic.
Real-time streaming of multimedia content over Internet protocol (IP) networks has become an increasingly common application in recent years. As noted above, 3G wireless networks will provide streaming data (both video and audio) to wireless devices for real time applications. A wide range of interactive and non-interactive multimedia Internet applications, such as news on-demand, live TV viewing, video conferencing, live radio broadcasting (such as Broadcast.com), and the like, will provide “real time” data streaming to wireless devices. Unlike a “downloaded” video file, which may be retrieved first in “non-real” time and viewed or played back later, real time (or streaming) data applications require a data source to encode and to transmit a streaming data signal over a network to a receiver, which must decode and play the signal (video or audio) in real time.
A wireless communication network comprises a plurality of cell sites (or “cells”). Each cell contains at least one base station (BS). Each base station contains at least one base transceiver station (BTS) and an antenna. Each base station (BS) is capable of communicating with a plurality of mobile stations (MS).
In IS-95 based systems and in IS-2000 based systems, each cell may comprise one or more sectors. Each cell is associated with a base transceiver station, and the base transceiver station is associated with the number of directional antennas. The number of antennas is equal to or greater than the number of sectors in a cell. For example, consider a cell that is divided into three sectors. Assume that the number of mobile stations within the cell is uniformly distributed throughout the cell. Further assume that the capacity of each cell in the network is N mobile stations. The capacity of a sector in a cell that has three sectors is N/3 mobile stations.
During a given period of time, each sector antenna in the base transceiver station (BTS) in the base station (BS) of a cell simultaneously transmits the same data signals to the N mobile stations within the cell. In a three sector cell, (1) a first sector antenna in the base transceiver station transmits a data signal to the N mobile stations, and (2) a second sector antenna in the base transceiver station simultaneously transmits the same data signal to the N mobile stations, and (3) a third sector antenna in the base transceiver station simultaneously transmits the same data signal to the N mobile stations.
This prior art arrangement has some disadvantages. For example, consider a base transceiver station that is transmitting data to a mobile station in a unicast transmission mode. In a unicast transmission mode the data transmission from the base transceiver station is intended only for the mobile station. The base transceiver station then receives data to transmit to the mobile station in a broadcast transmission mode. In a broadcast mode the data transmission from the base transceiver station is intended for all of the mobile stations in the cell.
Because the mobile station is receiving data traffic on its dedicated channel, the base transceiver station has to transmit both the unicast mode information and the broadcast mode information to the mobile station on the dedicated channel. The base transceiver station must use an algorithm that does not terminate the current data call to the mobile station. The required mapping causes the packet length to be too long. The long transmission may result in an undesirable transmission time delay or may result in an increased error rate for the data traffic. This problem could be solved if there were a way to transmit both the unicast mode information and the broadcast mode information to the mobile station within a period of time that is shorter than the period of time required by prior art methods.
The presently existing IS-95 and IS-2000 systems do not provide for concurrent data transmissions in a wireless communication network. Therefore, there is a need in the art for a system and method that is capable of providing concurrent data transmissions in a wireless communication network. In particular, there is a need for a system and method that is capable of enabling base transceiver stations in a cell of a wireless communication network to coordinate and simultaneously transmit concurrent data transmissions to the mobile stations in the cell.